1. Field of the Invention
The present invention is directed to a method and apparatus for automatically turning off a computer monitor when its associated computer is temporarily not in use, and for automatically turning the monitor on when use of the computer is resumed.
2. Description of the Prior Art
Computer systems generally consist of a computing unit 1 (which may have built-in storage devices like floppy disks, hard disks and tape drives), a keyboard 2 and a monitor 3, as schematically shown in FIG. 1. The computing unit 1 may also be connected with a printer and other peripheral devices.
These types of computing devices are often referred to as PC's (Personal Computers).
Another type of computing system is shown in FIG. 2, in this type of system a main computer 9 is connected to several terminals 10, such as by connection to the respective monitors 3, each with its own keyboard 2. The main computer 9 itself is typically more powerful than that of FIG. 1 in order to handle the workload from the combined group of terminals/monitors.
Several other configurations exist including a combination of FIG. 1 and FIG. 2, where each terminal 10 in FIGS. 2 actually consists of a computing device as shown in FIG. 1. This combination of centralized main unit and de-centralized PC-units is quickly gaining popularity among many data system users.
All these systems draw energy, and in many cases, the monitor itself uses a significant amount of energy to run properly. Typically, these systems stay on during the entire workday, even when they are not in active use. This means waste of energy. For a company with, approximately 500 employees each with his or her own PC, this power waste may easily reach many kilowatts every day. Heretofore, this has been accepted, but it is to be expected that much stricter requirements are going to be put on power conservation in computer systems in the future. This will be done both to save cost and also to protect the environment.
Although operators can be trained to turn the computer system off every time they leave their desk, most people will not find this practical. Therefore, system should be designed to perform this task automatically, and in a way which causes few, if any, problems or delays for the operator.
In principle, automatically saving energy by turning off the computer system is fairly easy. Small portable computers (laptop computers) have had such features for several years. The computer itself is designed so that if there is no activity from the keyboard or from other external inputs during a specified time, the computer shuts down as much as possible of its system to save energy. Only minimum logic is kept active to detect when the keyboard or other external inputs are becoming active again requiring that the rest of the computer system is turned on again.
In laptop computers, this power-saving feature is fairly simple to implement, since the monitor display is integrated with the computer system itself. However, for normal PC systems and similar systems as shown in FIGS. 1 and 2 in which the monitor is a separate item receiving the information to be displayed from the (separate) computer unit, the situation is more difficult. Because the computer unit must detect all activities from the keyboard or other internal/external sources, it is fairly easy to design the computer system itself so that a non-activity situation is detected and specified internal devices in the computer unit itself are turned off. However, turning off the external monitor automatically from the computer unit is much more difficult, since most monitor systems are based on very standardized data protocols operating at a very low "intelligence" level (EGA, VGA). The most common types of systems typically receive picture (video) information over a simple bus system where a few (3) lines transfer the color information (intensity) for each pixel or dot. Typically, these signals are analog. Additionally, synchronization signals such as vertical and horizontal synchronization are transferred either on separate digital lines or are embedded into the analog color lines (by driving the signal to a level "blacker than black" or "whiter than white"). FIG. 3 shows a simplified example using the very common VGA display mode. Monochrome monitors uses only the green line, with the red and the blue left inactive. FIG. 4 shows an example of synchronization pulses embedded in an analog color signal.
Such standardized video monitor systems contain no means for sending special commands over the same bus, i.e., but, for example, orders to turn the power on or off.
It would be possible in theory to design a video monitor system in which such special commands could be sent to the monitor to turn it on and off. These could either be sent on special lines, or on the same lines as the normal picture by using some special predefined commands. However, today's monitor systems are (as already mentioned) highly standardized. To introduce such a new system with special commands into today's standardized computer world would be very difficult insofar as commercial acceptance.
As already mentioned, the computer unit itself can fairly easily detect that a certain time has passed with no activities from the keyboard (or other internal/external sources) and can then for example, physically turn off the AC power to the terminal or video monitor. No special commands, etc. between the computer unit and the terminal are required to perform this task. However, such a system will have the serious drawback that the normal CRT monitor will require considerable time to warm up again when the computer system is reactivated.